1. Field of the Invention
The present invention relates to a method of manufacturing a printed circuit board (PCB) having a landless via hole, and more particularly, to a method of manufacturing a PCB having a landless via hole without the upper land of a via hole, using a photoresist (P-LPR) which is loaded in the via hole.
2. Description of the Related Art
With the development of electronic industries, an increase in the functionality of electronic parts and a decrease in the size thereof are increasingly required. In order to satisfy such requirements, PCBs also need a highly dense circuit pattern, thus various methods of realizing a fine circuit pattern have been devised and applied.
Among methods of forming a fine circuit pattern, the present invention adopts a method of realizing a highly dense circuit pattern having a landless via hole by removing the upper land of a via hole.
FIG. 1 is a perspective view schematically showing a conventional PCB 100 having a landless via hole, which was disclosed in U.S. Pat. No. 5,510,580 (granted on 23 Apr. 1996).
As shown in FIG. 1, a conventional PCB 100 is provided with a via hole structure having no upper land by forming a blind via hole 12 in the surface of a substrate 10 having an inner layer circuit 40 to connect it to the inner layer circuit 40 of the substrate 10, forming a conductive layer 32 on the inner wall of the blind via hole 12, and directly connecting the conductive layer to a circuit pattern 22 on the surface of the substrate.
Below, the method of manufacturing the PCB of FIG. 1 is briefly described with reference to the flowchart of FIG. 2.
As shown in FIGS. 1 and 2, the base substrate 10 having the inner layer circuit 40 is provided (S10), and the blind hole 12 is processed in the surface of the base substrate 10 so as to be connected to the inner layer circuit 40 of the base substrate 10 (S12). Subsequently, a conductive layer is formed on the surface of the base substrate including the blind hole 12 (S14).
Then, a photoresist is formed in the blind hole 12 (S16). As such, the photoresist is exemplified by a positive liquid photoresist (P-LPR). The photoresist is applied on the entire surface of the base substrate, cured, and exposed in a state of the portion thereof corresponding to the blind hole being masked, such that the photoresist remains only in the blind hole.
Thereafter, the conductive layer, which is formed on the surface of the base substrate 10, is removed. In this case, the conductive layer, which is present in the blind hole, is protected by the remaining photoresist (S18). Then, the photoresist, which remains in the blind hole, is removed (S20).
Subsequently, additional photolithography is conducted to thus form a circuit pattern 22 on the surface of the base substrate 10 (S22), thereby forming a PCB 200 having a landless via hole. As such, the circuit pattern 22 is characterized in that no upper land is formed around the blind hole 12.
Such a conventional PCB is advantageous in that no upper land need be formed. However, since a series of exposure and development processes is repeatedly performed in the processes of forming the conductive layer in the blind hole and of forming the circuit pattern on the surface of the base substrate, the manufacturing process is complicated, thus increasing the cost and process time period.